What are some of the starting phrases that I can use while responding to Ph.D examination committee questions during my defence?
In addition to Pete Clark's excellent answer, I would like to offer a second piece of advice. When you are feeling nervous or "put on the spot" by questions, an excellent first step is to begin by ensuring that you have understood the question. You can say something like:
"If I understand correctly, you are asking [paraphrased question]
and then go on with your response. This both makes sure you are clear about your communication as well as giving you a moment to steady your nerves and to think about your response.
Trying to prepare for any academic examination via stock phrases which are not related to the content of the subject is a very poor idea. You are never expected to know everything about your subject or be able to answer every question related to your work. When you do not know something, an ideal answer is "I don't know, but..." What follows should show that you know something related to the question and/or have some ideas about what you would do in order to learn the answer that you do not now possess.
I don't mean to be harsh, but in my opinion "while preparing for your PhD defense" is a bit late to be learning the above lesson and in particular that "polite and impressive phrases" will please no one. If I were on an exam committee and saw someone answering in this way, it would make a much more negative impression on me than a crisp, honest "I have no idea" (with no "but..."). If someone said that, then 90% of the time I would drop the line of inquiry and move on to something that they do know. If someone tried to blow smoke in my face, I might well try to wring an honest admission of lack of knowledge out of them. Please consider yourself warned.
Added: The clarified version of the question changes things a bit. I would still advise against memorizing specific phrases, as I think that could come off as trying to obfuscate (which, as above, would be very bad). It sounds like the OP may just be a bit nervous about an important presentation given in a non-native language. I certainly hope it is the case that the OP has given academic presentations before and has answered questions from faculty before. I would recommend that the OP talk to his advisor, to get some feedback about the format of the defense and to get some practice answering questions. In my opinion the precise words used to frame an answer to a question are not very important, and the less framing material and the more direct the answer, the better. But the OP can try out answering questions with his advisor, and if there is really some formal deficiency, his advisor can help him remedy it. This is part of the advisor's job. Getting stock phrases from the internet from those who don't know the OP or the subject of his thesis seems quite likely to backfire.
I need a list of some starting phrases for responding the examiner's question.
No you don't, what you need is good arguments to back your research claims - their validity, their novelty, their applicability/importance and so on.
Having said that, some universities have certain rules of protocol, e.g. examiners begin their questioning by reciting "By the permission of the esteemed [position-holder-here] and by my right, I will address several questions to the candidate" or something along these lines. It might be the case that there's some ceremonial opening for your reply. That kind of ceremony - like the robes, and hats, and the "procession" etc. are of symbolic but not material importance. Find some official involved with organizing the examination and have them tell you about the ceremonial procedure.
But again - it's the substance, not the form, which matters.